Shockable rhythms are specific heart rhythms that can cause sudden cardiac arrest, meaning the heart suddenly stops pumping blood. These rhythms happen when the heart’s electrical signals become irregular and out-of-sync, causing it to quiver or beat too fast without producing a pulse.
In cases of shockable rhythms, a treatment called defibrillation is used. Defibrillation sends a controlled electric shock through the heart to reset its rhythm to a normal one. This is done using an Automated External Defibrillator (AED), which can be found in many public places. AEDs are simple to use, even for people without medical training. Recognizing shockable rhythms and using an AED quickly can significantly increase a person’s chances of survival in a cardiac emergency.
Types of Shockable Rhythms
There are 2 main types of shockable rhythms:
- Ventricular fibrillation(VF), where the heart’s rhythm is irregular and disorganized
- Pulseless ventricular tachycardia(pVT), where the heart beats extremely fast and is unable to pump blood effectively.
Ventricular Fibrillation (VF)
Ventricular fibrillation (VF) is a very serious heart rhythm where the heart’s electrical signals become completely irregular. Instead of the heart’s lower chambers (ventricles) contracting normally to pump blood, they start to quiver or shake wildly. This means the heart can’t pump blood to the body, leading to sudden cardiac arrest. Without quick action, such as defibrillation, VF can be fatal within minutes.
Causes of Ventricular Fibrillation:
- Coronary artery disease
- Heart attack (Myocardial infarction)
- Cardiomyopathy (heart muscle disease)
- Electrolyte imbalances (e.g., low potassium or magnesium)
- Congenital heart defects
- Severe trauma or injury to the chest
- Drug overdoses (especially stimulants or antiarrhythmic drugs)
- Heart surgery or procedures
- Severe hypothermia
Symptoms of Ventricular Fibrillation:
- Sudden collapse and loss of consciousness
- No pulse or weak, irregular pulse
- No breathing or abnormal breathing (gasping)
- Chest pain or discomfort (in some cases prior to collapse)
- Dizziness, lightheadedness, or fainting (may occur before collapse)
Pulseless Ventricular Tachycardia (pVT)
Pulseless ventricular tachycardia (pVT) happens when the heart beats extremely fast in the ventricles, but it’s so rapid that the heart doesn’t have enough time to fill with blood before it beats again. As a result, the heart can’t pump blood properly, and the person collapses. pVT is a very serious condition that also causes sudden cardiac arrest and needs immediate treatment to restore a normal rhythm.
Causes of Pulseless Ventricular Tachycardia:
- Heart attack (myocardial infarction)
- Coronary artery disease
- Cardiomyopathy (weakened heart muscle)
- Severe electrolyte imbalances (e.g., potassium or magnesium abnormalities)
- Drug toxicity (e.g., certain antiarrhythmic drugs, stimulants)
- Structural heart diseases
- Previous heart surgery or trauma
Symptoms of Pulseless Ventricular Tachycardia:
- Sudden collapse and loss of consciousness
- No pulse or very weak, rapid pulse
- No normal breathing or irregular gasping breaths
- Dizziness or fainting (may occur before collapse)
- Chest pain or discomfort (may occur in some cases before collapse)
How to Respond to Shockable Rhythms in Adult Cardiac Arrest?
When a person experiences sudden cardiac arrest due to shockable rhythms like ventricular fibrillation (VF) or pulseless ventricular tachycardia (pVT), it’s crucial to follow the Adult Cardiac Arrest Algorithm for the best chance of survival. This algorithm provides a clear, step-by-step process for healthcare providers and first responders in emergencies.
The first step is recognizing the shockable rhythm using an ECG or by monitoring the person’s condition. Once identified, immediate defibrillation is performed using an Automated External Defibrillator (AED) or a manual defibrillator. This delivers an electric shock to the heart, helping reset its electrical activity and restore a normal rhythm. After the shock, CPR is resumed to keep blood flowing to vital organs. If the rhythm does not return to normal, additional defibrillation or advanced interventions, such as medications, may be required.
It’s essential to continue CPR and monitor the patient’s rhythm until the heart regains a regular beat or emergency medical professionals take over. The sooner defibrillation is performed, ideally within the first few minutes of cardiac arrest, the higher the chance of survival.
ACLS Guidelines for Treating Shockable Rhythms
The 2018 American Heart Association (AHA) guidelines recommend immediate defibrillation for ventricular fibrillation (VF) or pulseless ventricular tachycardia (pVT), followed by high-quality CPR to keep blood flowing. If the shock doesn’t fix the rhythm, epinephrine is given to help circulation, and antiarrhythmic drugs like amiodarone or lidocaine may be used. These drugs have not shown long-term survival benefits but can increase the return of spontaneous circulation (ROSC). CPR and defibrillation should continue until a normal rhythm is restored or more advanced care is available.
Challenges and Considerations in Treating Shockable Rhythms
Shockable rhythms are fatal and come with challenges as well. One of the main challenges is the timing. Early defibrillation is a must and providing shock can reduce the chances of survival. AED should also be accessed easily. Responders can sometimes have difficulty finding the equipment, and location can be a major barrier. Another challenge is ensuring high-quality CPR, as poor chest compression can decrease blood flow and reduce the effectiveness of defibrillation.
Additionally, some patients may have underlying health conditions that may require careful consideration of medication and advanced intervention, which may further complicate the treatment.
Conclusion
In summary, heart rhythms that are shockable, such as ventricular fibrillation (VF) and pulseless ventricular tachycardia (pVT) are life-threatening conditions and require immediate recognition and treatment. These shockable rhythms prevent the heart from pumping blood and lead to cardiac arrest. Defibrillation, coupled with high-quality CPR and appropriate medications, is key to restoring a normal heart rhythm and improving the chances of survival.
The ACLS guidelines offer a clear, structured approach to managing shockable rhythms. At Heart Start CPR, we offer comprehensive ACLS training that helps you with the knowledge and skills to respond confidently in cardiac emergencies. By enrolling in our ACLS course in San Francisco, you’ll be ready to apply these life-saving protocols and make a critical difference in the outcome of cardiac arrest cases caused by shockable rhythms.
